I. Field of the Invention
The instant invention pertains to vehicle suspension systems and more particularly to such systems which facilitate vehicle travel over uneven terrain and which lock the suspension against movement to stabilize the vehicle when it stops.
II. Description of the Related Art
Excavating and construction machines such as backhoes, cranes and the like are used to lift loads, such as dirt or construction materials. Some such vehicles may be used to apply large forces to other objects as when a wrecking ball is suspended from a crane which is used to demolish a building.
Such vehicles incorporate suspension systems to facilitate vehicle travel. Some of these vehicle suspensions permit large amounts of relative movement between the suspension and the vehicle frame to facilitate travel over uneven terrain.
When such a vehicle is driven to the location at which it is to be used, it is important to fix the suspension system relative to the vehicle frame prior to lifting loads and/or otherwise applying force to effect proper and safe operation.
One type of vehicle incorporating a prior art suspension lock system is shown in U.S. Pat. No. 4,763,742 for a Tree Feller-Buncher, which is incorporated herein by reference and which is assigned to the assignee of this application. Generally speaking, the prior art Feller-Buncher comprises a four-track vehicle especially adapted for logging on steep slopes. Two of the tracks are mounted on opposing pivot arms which extend transversely outwardly from opposing sides of the vehicle frame and pivot therefrom. The other two tracks are fixed relative to the frame. The arms are linked together in such a way so that upward movement of one arm causes downward movement of the other arm, thereby tending to maintain the frame in an attitude parallel to the fixed tracks as the vehicle traverses a slope.
The prior art Feller-Buncher includes an articulated, extensible arm which is adapted for severing, bunching and moving trees and bunches of trees. In some applications, it is important to lock the pivot arms against pivoting movement when the articulated arm is used in order to stabilize the vehicle.
The prior art Feller-Buncher incorporated a pawl pivotally mounted on each pivot arm which could be selectively engaged and disengaged with one of a plurality of teeth formed on the frame thereby preventing upward movement of both pivot arms. The foregoing prior art vehicle suspension lock system is designed to permit the vehicle operator to lock the suspension from the vehicle controls rather than leaving the vehicle to install and/or adjust stabilizing arms or the like.
It would be desirable to utilize a vehicle suspension lock system which has fewer mechanical parts and which is less exposed to the brush and dirt encountered during operation of a tree feller-buncher than prior art systems. Such a system would require less maintenance and would be more reliable than prior art vehicle suspension lock systems.